Organic electroluminescence display panel and method for sealing the same

ABSTRACT

An organic EL display panel has a multi-layered structure in which a first electrode and a second electrode are formed on a transparent panel and an organic EL layer is formed between the first and second electrodes. A method for sealing the organic EL display panel includes the steps of forming a buffer layer of an organic matter such as silicon oxide and silicon nitride on the transparent panel, and locating a shield cover on the buffer layer. Thus, adhesive strength between the panel and an adhesive is enhanced to prevent external humidity and oxygen from being permeated into the panel, thereby increasing life span of the display.

This application is a continuation of U.S. application Ser. No.10/627,816 filed Jul. 28, 2003, now U.S. Pat. No. 7,011,562 which is adivisional of U.S. application Ser. No. 09/783,964 which was filed Feb.16, 2001 and which now has issued as U.S. Pat. No. 6,624,472 on Sep. 23,2003. The disclosures of the previous applications are incorporated byreference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic electroluminescence (EL)display panel, and more particularly to an organic EL display panel anda method for sealing the same.

2. Description of the Related Art

Recently, with a large sized tendency of a display device, request for aflat display occupied in a small space is increasing. As an example ofthe flat display, an EL display is receiving much attention.

The EL display is divided into an inorganic EL display and an organic ELdisplay in accordance with its materials. Of them, the organic ELdisplay emits light while electrons injected into an organic EL layerare combined with a hole and erased. The organic EL layer is formedbetween a cathode and an anode.

The organic EL display has an advantage in that it is driven at a lowervoltage (for example, about 10V or less) than a voltage of a plasmadisplay panel (PDP) or an inorganic EL display. Also, since the organicEL display has further advantages such as a wide viewing angle, highspeed reactivity, and high contrast, it is used as a pixel of a graphicdisplay, a television video display, and a surface light source.Moreover, since the organic EL display is thin and weighs light, and itscolor sensitivity is good, it is suitable for a next generation flatdisplay.

However, the most serious problem in commercially using the organic ELdisplay is that its life span is short.

The life span of the display is determined by various factors such asimpurities within organic matters, interface between the organic mattersand electrodes, a low crystallization temperature (Tg) of the organicmatters, and oxidation of the display due to oxygen and humidity.Problems related to such factors can be solved by refinement of theorganic matters, development of a material having a high crystallizationtemperature, and induction of an organic metal to the interface betweenthe electrodes and the organic matters. However, it is difficult tosolve the problem related to oxidation of the display due to oxygen andhumidity.

Oxygen and humidity that oxidize the display may exist in the display ormay externally be permeated during the fabricating process steps. Oxygenand humidity are permeated into a pinhole of the display and oxidize anorganic film and metal, thereby failing to perform a light emittingfunction of the display.

In the related art, to solve this problem, the display is covered with ashield glass to externally cut off humidity and oxygen.

In other words, as shown in FIGS. 1 a and 1 b, an organic EL displayprovided with a glass panel 1, a first electrode 2, an organic EL layer3, and a second electrode 4 is covered with a shield glass 5 to cut offhumidity and oxygen.

The shield glass 5 is attached to a corner portion of the panel by anadhesive 6.

However, since adhesive strength of the adhesive 6 is not good for aglass panel, the adhesive 6 is detached from the panel after a constanttime elapses.

If the adhesive 6 is detached from the panel, a gap occurs between thepanel and the adhesive so that humidity or oxygen is permeated into thedisplay. For this reason, a problem arises in that life span of thedisplay is shortened.

SUMMARY OF THE INVENTION

To solve the above problems, an object of the present invention is toprovide an organic EL display panel and a method for sealing the same,in which life span of the display can be improved by adhesive strengthbetween a panel and an adhesive.

To achieve the above object, in an organic EL display panel having amulti-layered structure in which a first electrode and a secondelectrode are formed on a transparent panel and at least one organic ELlayer is formed between them, the organic EL display panel according tothe present invention includes a buffer layer formed on the transparentpanel and a shield cover located on the buffer layer.

In another aspect, in a method for sealing an organic EL display panelhaving a multi-layered structure in which a first electrode and a secondelectrode are formed on a transparent panel and an organic EL layer isformed between the first and second electrodes, the method for sealingan organic EL display panel according to the present invention includesthe steps of forming a buffer layer on the transparent panel, andlocating a shield cover on the buffer layer.

The buffer layer is formed on an entire surface of the panel other thana tap bonding region and a pixel region of the first and secondelectrodes, or only on the panel of a region where the shield cover islocated on the transparent panel, or both on the panel of a region wherethe shield cover is located and on the electrode of a region where theshield cover is located.

Also, the buffer layer of the region where the shield cover is locatedhas an uneven shape or a dot shape. The dot shaped buffer layer isformed of any one of a round shape, a triangle shape, a quadrangleshape, a polygonal shape, and so on.

The buffer layer of the region where the shield cover is located and thebuffer layer of a region other than the region where the shield cover islocated have the same material as each other or a different materialfrom each other. In other words, the buffer layer of the region wherethe shield cover is located includes a material of either silicon oxideor silicon nitride, while the buffer layer of the region other than theregion where the shield cover is located includes a material of siliconoxide, silicon nitride, polyimide, or polyacryl.

In the present invention, an inorganic material such as silicon oxideand silicon nitride is formed on the panel of the region where theshield cover is located, so that adhesive strength between the panel andthe adhesive is enhanced to prevent external humidity and oxygen frombeing permeated into the panel, thereby increasing life span of thedisplay.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, characteristic features and advantages of the presentinvention will now become apparent with a detailed description of anembodiment made with reference to the accompanying drawings, in which:

FIGS. 1 a and 1 b are a plane view and a sectional view showing arelated art method for sealing an organic EL display panel;

FIGS. 2 a and 2 b are a plane view and a sectional view showing a methodfor sealing an organic EL display panel according to the firstembodiment of the present invention;

FIG. 3 shows various uneven shapes of a buffer layer of FIG. 2 a;

FIGS. 4 a and 4 b are a plane view and a sectional view showing a methodfor sealing an organic EL display panel according to the secondembodiment of the present invention; and

FIGS. 5 a and 5 b are a plane view and a sectional view showing a methodfor sealing an organic EL display panel according to the thirdembodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following is a detailed description of a preferred embodiment of anorganic EL display panel and a method for sealing the same according tothe present invention made with reference to the accompanying drawings.

FIGS. 2 a and 2 b are a plane view and a sectional view showing a methodfor sealing an organic EL display panel according to the firstembodiment of the present invention.

As shown in FIGS. 2 a and 2 b, to form an organic EL display, atransparent conductive film such as Indium Tin Oxide (ITO) is formed ona transparent insulating panel 11 such as glass. The transparentconductive film is patterned by photolithography process to form firstelectrodes 12 having a plurality of stripes and contact pads 12-1 forcontact with second electrodes which will be formed later.

A buffer layer 13 is formed on an entire surface of the panel other thana tap bonding region 20 and a pixel 21 of the first electrode 12 and thecontact pads 12-1.

The buffer layer 13 acts different depending on its formation position.In other words, a function of the buffer layer formed in a cornerportion of the panel 11 is different from that of the buffer layerformed around the pixel region.

The buffer layer formed in a corner portion of the panel 11 acts toenhance adhesive strength of an adhesive when a shield cover is attachedto the panel. The buffer layer formed around the pixel region acts toperform electrical insulation between the first electrode and the secondelectrode and between the second electrodes.

A region of the buffer layer formed in a corner portion of the panel 11(i.e., a region where the shield cover is located) may have an unevenshape or a dot shape, as shown in FIG. 3, to enhance adhesive strengthof the adhesive.

That is, the dot shaped buffer layer may be formed of any one of variousshapes such as a round shape, a triangle shape, a quadrangle shape, anda polygonal shape.

The buffer layer formed around the pixel region may have a stripe shapein a direction orthogonal to the first electrode 12. As described above,since the buffer layer 13 acts differently depending on its position,one material or different materials may be used as the buffer layer 13.

In other words, the material of the buffer layer formed in a cornerportion of the panel (buffer layer of a region where the shield cover islocated) is an inorganic matter such as silicon oxide and siliconnitride. The material of the buffer layer formed around the pixel region(buffer layer of a region other than the region where the shield coveris located) may be either an inorganic matter such as silicon oxide andsilicon nitride or an organic matter such as polyimide, and polyacryl.

At this time, the buffer layer has a thickness of about 0.1˜5 μm.

Next, for electrical insulation between second electrode stripes whichwill be formed later, electrical insulation barrier stripes 14 areformed on the buffer layer 13.

Subsequently, organic EL layers 15 are formed on the electricalinsulation barrier stripes 14.

The organic EL layers 15 are formed to be wider than an entirelight-emitting region (an entire region where the first and secondelectrodes cross orthogonally). However, the organic EL layers 15 shouldbe formed inwardly rather than end portions of the contact pads 12-1.

A conductive material such as Al, Mg:Ag, and Al:Li is formed to formsecond electrodes 16. Thus, the fabrication of the organic EL display iscompleted.

Here, the second electrodes 16 are formed to be wider than thelight-emitting region and to be connected with the contact pads 12-1.

Subsequently, the organic EL display is covered with a shield cover 17to cut off humidity and oxygen. The shield cover 17 is attached to thebuffer layer 13, which is formed in a corner portion of the panel, by anadhesive 18. A UV hardening high molecular substance is used as theadhesive 18. In addition, other adhesives such as a thermal hardeningadhesive or an inorganic adhesive may be used.

After the buffer layer is formed as described above, if the shield coveris attached to the buffer layer by the adhesive, adhesive strength ofthe adhesive is enhanced, thereby failing to permeate external humidityor oxygen into the organic EL display.

FIGS. 4 a and 4 b are a plane view and a sectional view showing a methodfor sealing an organic EL display panel according to the secondembodiment of the present invention.

In the second embodiment of the present invention, a buffer layer isonly formed on a panel of a region where a shield cover is located.

Generally, since a sealing adhesive does not have good adhesive strengthwith the panel, the buffer layer is formed on only the panel of theregion where the shield cover is located.

Also, the buffer layer may have an uneven shape or a dot shape toenhance adhesive strength of the adhesive in the same manner as thefirst embodiment.

In the second embodiment, since the buffer layer is only formed on thepanel of the region where the shield cover is located, the process issimplified. However, in this case, either a display structure which doesnot require an electrical insulation barrier or a display structurewhich enables electrical insulation between second electrodes by anelectrical insulation barrier only without a buffer layer is required.

FIGS. 5 a and 5 b are a plane view and a sectional view showing a methodfor sealing an organic EL display panel according to the thirdembodiment of the present invention.

In the third embodiment of the present invention, a buffer layer isformed on both a panel of a region where a shield cover is located andan electrode of a region which the shield cover is located.

Also, the buffer layer may have an uneven shape or a dot shape toenhance adhesive strength of the adhesive in the same manner as thefirst embodiment.

In the third embodiment, the process is also simplified. However, eithera display structure which does not require an electrical insulationbarrier or a display structure which enables electrical insulationbetween second electrodes by an electrical insulation barrier onlywithout a buffer layer is required.

As aforementioned, the organic EL display panel and the method forsealing the same according to the present invention have the followingadvantages.

The inorganic matter such as silicon oxide and silicon nitride is formedon the panel of the region where the shield cover is located, so thatadhesive strength between the panel and the adhesive is enhanced toprevent external humidity and oxygen from being permeated into thepanel, thereby increasing life span of the display.

The above description will enable one skilled in the art to modify andrevise the invention within the spirit not degrading the technicalconcept of the present invention. However, the technical scope of thepresent invention is not limited to the above description of theembodiment but shall be determined by the claims.

1. An EL device comprising: an insulating panel; electrodes formed onthe insulating panel; a shield cover located in a spaced apart relationfrom the insulating panel and the electrodes; a non-conductive bufferlayer formed on at least a portion of the electrodes and the insulatingpanel in a surrounding region of the shield cover; and an adhesive layerlocated between the buffer layer and the shield cover to attachmentbetween the insulating panel and the shield cover.
 2. The EL device asclaimed in claim 1, wherein the EL device is a television, computer,monitor or graphic display.
 3. The EL device as claimed in claim 1,wherein the material of the buffer is either silicon oxide or siliconnitride.
 4. The EL device as claimed in claim 1, wherein the bufferlayer increases the adhesive strength between the insulating panel andthe shield cover, and prevents from permeating external humidity oroxygen.
 5. The EL device as claimed in claim 1, wherein the buffer layerhas an uneven or discontinuous surface.
 6. The EL device as claimed inclaim 1, wherein the buffer layer has a thickness of about 0.1–5 μm. 7.The EL device as claimed in claim 1, wherein the electrodes are contactpads for connecting with an external power source.
 8. The EL device asclaimed in claim 1, wherein the electrodes are anode lines or cathodelines.
 9. The EL device as claimed in claim 1, wherein the electrodesare gate lines, source lines or drain lines.
 10. An EL devicecomprising: an insulating panel; electrodes formed on the insulatingpanel; a shield cover located in a spaced apart relation from theinsulating panel and the electrodes; a first buffer layer formed on atleast a portion of the electrodes and the insulating panel in asurrounding region of the shield cover; a second buffer layer fanned onat least a portion of the electrodes and the insulating panel in amiddle region of the shield cover; and an adhesive layer located betweenthe first buffer layer and the shield cover to attachment between theinsulating panel and the shield cover.
 11. The EL device as claimed inclaim 10, wherein the second buffer layer performs electrical insulationbetween the electrodes.
 12. The EL device as claimed in claim 10,wherein the first buffer layer and the second buffer layer comprise thesame or different materials each other.
 13. The EL device as claimed inclaim 10, wherein the material of the first buffer is either siliconoxide or silicon nitride, while the material of the second buffer is anyone of silicon oxide, silicon nitride, polyimide, and polyacryl.
 14. TheEL device as claimed in claim 10, wherein the first buffer layerincreases the adhesive strength between the insulating panel and theshield cover, arid prevents from permeating external humidity or oxygen.15. An EL device comprising: an insulating panel; first electrodesformed on the insulating panel; at least one of EL layers formed on thefirst electrodes; second electrodes formed on the at least one of ELlayers; a shield cover located in a spaced apart relation from theinsulating panel and the electrodes; a first buffer layer formed on atleast a portion of the first electrodes and the insulating panel in asurrounding region of the shield cover; a second buffer layer formed atleast a-portion -of the first electrodes and the insulating panel in amiddle region of the shield cover; and an adhesive layer located betweenthe first buffer layer and the shield cover to attachment between theinsulating panel and the shield cover.
 16. The EL device as claimed inclaim 15, wherein the second buffer layer performs electrical insulationbetween the first electrode and the second electrode and between thesecond electrodes.
 17. The EL device as claimed in claim 15, furthercomprising: electrical insulation barrier stripes located on the secondbuffer layer between the second electrodes.
 18. The EL device as claimedin claim 15, wherein the first buffer layer and the second buffer layercomprise the same or different materials each other.
 19. The EL deviceas claimed in claim 15, wherein the material of the first buffer iseither silicon oxide or silicon nitride, while the material of thesecond buffer is any one of silicon oxide, silicon nitride, polyimide,and polyacryl.
 20. The EL device as claimed in claim 15, wherein thefirst buffer layer increases the adhesive strength between theinsulating panel and the shield cover, and prevents from permeatingexternal humidity or oxygen.
 21. An EL device comprising: an insulatingpanel; first electrodes formed on the insulating panel; at least one ofEL layers formed on the first electrodes; second electrodes formed onthe at least one of EL layers; a shield cover located in a spaced apartrelation from the insulating panel and the electrodes; a buffer layerformed on an entire surface of the insulating panel and the firstelectrodes other than a tap bonding region and a pixel region of thefirst electrodes; and an adhesive layer located between the buffer layerarid the shield cover to attachment between the insulating panel and theshield cover.
 22. The EL device as claimed in claim 21, wherein thebuffer layer performs electrical insulation between the first electrodeand the second electrode and between the second electrodes.
 23. The ELdevice as claimed in claim 21, further comprising: electrical insulationbarrier stripes located between the second electrodes.
 24. The EL deviceas claimed in claim 21, wherein the buffer layer is non-conductive. 25.The EL device as claimed in claim 21, wherein the material of the bufferis any one of silicon oxide, silicon nitride, polyimide, and polyacryl.26. The EL device as claimed in claim 21, wherein the buffer layerincreases the adhesive strength between the insulating panel and theshield cover, and prevents from permeating external humidity or oxygen.